Method of discharging solids and gases from a fluidized bed



06L 3 c. E. LESHER METHOD OF DISCHARGING SOLIDS AND GASES FROM AFLUIDIZED BED Filed July 22, 1948 FIG. 2

FIG.

INVENTOR C. E. LESHER Q35 12% M;

ATTORNEY Patented Oct. 6, 1953 METHOD OF DISCHARGING SOLIDS AND GASESFROM A FLUIDIZED BED Carl E. Lesher, Ben Avon Heights, Pa., assignor toPittsburgh Consolidation Coal Company, Pittsburgh, Pa., a corporation ofPennsylvania Application July 22, 1948, Serial No. 40,066

2 Claims.

This invention relates to methods and apparatus for treating gases andsolids and, more particularly, to methods and apparatus for effectingseparation of gases and solids.

In gas-solids contacting systems wherein gas (as used herein I includevapors within the meaning of the term gas) is continuously withdrawnfrom a contacting zone, an appreciable amount of finely divided solidsor dust is carried out of the contacting zone by the withdrawn orefiiuent gas. It is customary practice to provide a separator such as acyclone above the contacting zone for separating the entrained dust fromthe gases. In those systems where the contacting zone is maintained atan elevated temperature, there frequently is sufiicient temperature dropfrom the contacting zone to the separator to result in condensation ofsome, at least, of the efiluent vapors or gases on the walls of theseparator. The presence of liquid condensate promotes gradual depositionand accumulation of extremely fine particles of solid on the walls ofthe separator to the point where they obstruct the passage of gasesthrough the separator. If the liquid condensate is carbonizable at thetemperatures existing on the walls of the separator then coking willtake place with consequent additional accumulation of solids within theseparator. Accordingly, it would be highly desirable if a separationzone could be provided which would operate under such conditions that nocondensation of gases would take place and no adherent solid depositswould collect on the walls.

The primary object of this invention is to provide an improved methodand apparatus for treating gases and solids.

Another object of the present invention is to provide an improved methodand apparatus for effecting separation of gases and solids issuing froma contacting zone.

In accordance with my invention, the gases and solids coming from acontacting zone are separated in a separation zone which is disposedentirely beneath the level of the solids maintained in the contactingzone. The gases issuing from the contacting zone as well as the dustcontained in these elfiuent gases are circulated down through theseparation zone. Since the latter zone is surrounded by the contactingzone the two zones will be at substantially the same temperature withthe result that little or no condensation of gases occurs in theseparation zone. The separated gases are then withdrawn from theseparation zone to suitable points of purification or collection.

In the preferred embodiment of my invention, not only the efiiuent gasesand entrained dust pass through the separation zone but also any solidmaterial in excess of that required to maintain the desired bed level inthe contacting zone. This may be accomplished by arranging the inlet tothe separation zone at the desired bed level and by extending the outletof the separation zone to the exterior of the contacting zone. Forefficient operation in this preferred embodiment the bed of solidsshould be in a fluidized state in order to permit ready overflow ofsolids into the separation zone. The circulation through the separationzone of these excess solids produces a scouring of the interior walls ofthe separation zone so that accumulation of fine dust is prevented.

For a better understanding of my invention, reference should be had tothe following description and drawings in which:

Figure 1 is a diagrammatic illustration of a preferred embodiment of theapparatus of my invention;

Figure 2 is a diagrammatic illustration of a modification of thepreferred apparatus shown in Figure 1.

Referring specifically to Figure 1 of the drawings, numeral itdesignates a stationary vertical vessel adapted to enclose a contactingzone 12. Conduit I l communicates with the bottom of the vessel IE3 forintroducing solids and gases into the contacting zone. Th top of thevessel It is closed by a wall It. Disposed within the vessel it andentirely immersed in the contacting zone is a separator l8 which ispreferably of the cyclone type. Communicating with the separator 58 is aconduit 21! which extends from the top of the separator to a pointadjacent the top Wall It. A conduit 22 extends from the top of theseparator It to the exterior of the vessel It). A third conduit 24communicates with the bottom of the separator l8 and likewise extends tothe exterior of the vessel 10.

Referring to Figure 2 of the drawings, numeral 60 designates a vessel ofthe same type as disclosed in Figure 1 which is adapted to enclose acontacting zone 62. A conduit 64 communicates with the bottom of thevessel to for introducing gases and solids into the contacting zone. Awall 66 extends across the top of the vessel 50. Disposed within thevessel and immersed entirely in the contacting zone are two separatorsB8 and i0, preferably of the cyclone type. A conduit '52communicateswith the top of separator 58 and extends into the spacebetween of-the contacting zone.

the top wall 65 and the level of solids in the contacting zone. A secondconduit 14 extends from the top of the separator 68 to the top ofseparator w while a conduit 16 leads from the top of separator 10 to theexterior of the vessel 60. Conduits l8 and 80 are connected to thebottoms of separators 68:1and-T'0,.respectively,: and open into thecontacting zone 62 for discharging separated solids thereto. A dischargeconduit 82 is also provided in the lower portion of vessel 60 for re.-moving solids from the contacting zone.

For purposes of illustration only-,jthe operation of apparatus shown inFigures 1, and 'z' will be described in connection with carbonization ofbituminous coal. Howeven it shouldibe under stood that not only is theapparatus-:andmcthod herein described applicable to the treatment ofcoal generally, but also to any systems wherein it is desired to contactgases and solids r-andz-sub-- sequently separate the gaseous and solidproducts. Referring toFigure 1, finely divided bituminous coal isintroduced through conduit "14 into-the contactingzone L2 along with.steam.

The velocity of the steam introduced into .the

contactingzone isregulated so-that a.fluidized biedof finely'div-ided.carbonaceous solidsis maintained within the-contacting zone L0. Thecon.-

ditions required to establish this fluid state are well known in the artand form no part of the present invention.

The temperature-of the steam introduced into the contacting-zone is suchthat an average temperature is established in the contacting zone withinthe oarbonization range of 700 .F. to

1400 F. The finely divided coalis carbonized r Since separator 1-8 iscompletely immersed, in f the contacting zone 12, the temperaturemaintained therein .issubstantially thesame as that Consequently, little.or

no condensation of any of the gaseous products from the distillation ofthecoal takes place in the separator. These gaseous products .areconducted from vessel i0 intov conduit .22 to any suitable placeofdisposition. At the same time,

the precipitated fines'or dust,.as Well asv any char overflowing fromthe fluid bed are carried off throughconduit 24. .The char which issubstantially the same size-as the. .coal introduced into thercontactingzone serves to scour .the walls of the separator 18.. Thisscouringaction prevents accumulation of dust on the walls of the separator. Atthesame time, theexterior walls of the separator are maintained in .aclean condition by the scouring action of the finely divided coalmixtures surroundingthe separator. It will thus be seen that,theapparatus shown in .Figure 1 provides for maintaining a constantlevel offluidized solids .in thecontactingizoneand at the same timeprovides for clean separation of gaseous and solid products withoutplugging of the separator.

the-separators; The coal andheating "gas such as :steamare introducedin'tothe vessel 60 through conduit 64. A fluidized bed of the coal andresulting carbonaceous distillation residue may be established in thewell known manner to form *thecontactingzone 62. The level of the bed ismaintained by withdrawing solids in regulated .:amounts through conduit82. The efiluent gases aand entramed solid fines are conducted byconduit. l2 totseparator' 68 and to separator Ill by conduit l4.Theggases and solids are separated in these two separators in anysuitable manner with -.t-he- 1solids being returned to the contactingzone through conduits 1'8 and 80. The separated gases are withdrawn fromthe vesselthroughconrduit 16 .for purification, .etc.

According to. the provisions -of the. .patent statutes, I have explainedthe principle. preferred construction, and mode of operation of myinvention .and have. illustrated and described whatl now consider torepresent its best embodiment. However, I desire to have it understoodthat, within. the scope of the appended claims, the invention may bepracticed otherwise than as specifically illustrated and described.

.1. Method of treating solids and gases which comprises circulatinggases through a bed of finely. divided carbonaceous solids :underfluidiz- '.ing conditions a confined contacting zone which is maintainedat .carbonization tempera- .ture, conducting the emuentgases,includingthe tarry vaporous products, and entrained solids iromsaidcontacting zone. through said bed in heatexchange relation therewith,separating the solids andgases while being, conducted through .said bed.and withdrawing said separatedgases .irom. said. confined zone.

2. Method of .treatingsolids and gases which comprisescirculating,gases. througha bedof fine.- -ly divided carbonaceous solids under.fiuidizin conditions .ina confined contacting zone which is maintainedI at=carbonization temperature, con,- ducting the .gases, including thetarry vaporous productsof .carbonization, escaping from the top ,oIisaid.bedandall solids above a predetermined level down through said bed outof direct contact with said bed but in heat exchange relation with saidbed, .separatingthe solids and gases while being so circulated through.the bed, and withdrawing said separated solids and gasesirom said.fiuidized bed.

CARLTE. LESHER.

References Cited in the file ofthis patent UNITED STATES PATENTS NumberName .Date,

12,304,128 Thomas s Dec. '8, 1942 12,327,175 Conner -Aug. 1'7, 19432,367,281 Johnson Jan. 16, 1945 2379,448 Linn July 3, 1945 2,414,586'Egloff Jan. 21, 1947 2,429,751 Gohr Oct. 28, 1947 2,432,298 Eastwood eta1. Dec. 9;, 194.7

2. METHOD OF TREATING SOLIDS AND GASES WHICH COMPRISES CIRCULATING GASESTHROUGH A BED OF FINELY DIVIDED CARBONACEOUS SOLIDS UNDER FLUIDIZINGCONDITIONS IN A CONFINED CONTACTING ZONE WHICH IS MAINTAINED ATCARBONIZATION TEMPERATURE, CONDUCTING THE GASES, INCLUDING THE TARRYVAPOROUS PRODUCTS OF CARBONIZATION, ESCAPING FROM THE TOP OF SAID BEDAND ALL SOLIDS ABOVE A PREDETERMINED LEVEL DOWN THROUGH SAID BED OUT OFDIRECT CONTACT WITH SAID BED BUT IN HEAT EXCHANGE RELATION WITH SAIDBED, SEPARATING THE SOLIDS AND GASES WHILE BEING SO CIRCULATED THROUGHTHE BED, AND WITHDRAWING SAID SEPARATED SOLIDS AND GASES FROM SAIDFLUIDIZED BED.